JP2018527976A - How to ventilate a dialysis machine - Google Patents

Abstract

The present invention relates to a method for venting a dialyzer having a dialysate chamber, a blood chamber and a semi-permeable dialysis membrane separating the two chambers, and after filling the dialysate chamber and before filling the blood chamber. In order to remove air inclusions located in the face of the membrane on the dialysate chamber side, an overpressure against the blood chamber is generated in the dialysate chamber.
[Selection] Figure 1

Description

  The present invention relates to a method for venting a dialysis machine, and more particularly to a method for removing air inclusions located on the surface of a membrane on the dialysate chamber side after filling the dialysate chamber within a priming framework. The invention further relates to a dialysis machine having a control unit in which an algorithm for performing such a method is stored.

  Air inclusions located in the dialysis membrane have the result that mass transfer (diffusion) cannot take place at corresponding points during dialysis. The membrane surface is therefore lost to the treatment and the treatment efficiency (clearance) is reduced.

  The dialysis machine is primed prior to performing the dialysis process, and the dialysate chamber and blood chamber of the dialyzer are filled with priming fluid. The problem of air inclusions located in the dialysis membrane often occurs especially when filling the dialysate chamber of a capillary dialysis machine. These air contents can be removed only by user intervention after filling.

  For avoiding or removing such air inclusions, it is known to fill the dialysate chamber from the bottom to the top and optionally tap the dialyzer in addition thereto. The dialyzer must then be rotated to fill the blood chamber.

  Yet another known method provides for filling the dialysate chamber from top to bottom, which has the advantage that the dialyzer does not need to be rotated by the user to fill the blood chamber. However, a relatively low filling rate is important for good results and a small amount of air also remains in the dialysate chamber in this case.

  It is an object of the present invention to provide an improved method for venting a dialysis machine.

  This object is achieved according to the invention by the method according to claim 1. Accordingly, a method is provided for venting a dialyzer having a dialysate chamber, a blood chamber, and a semi-permeable dialysis membrane that separates the two chambers. Within the framework of the method, after filling the dialysate chamber and before filling the blood chamber, overpressure on the blood chamber is applied to the dialysate to remove air inclusions located on the face of the membrane on the dialysate chamber side. Generated in the chamber.

  Overpressure in the dialysate chamber relative to the blood chamber can also be generated in that a vacuum is generated in the blood chamber. It can also occur, for example, in that the blood chamber is vented and an overpressure to atmospheric pressure is generated in the dialysate chamber.

  “Overpressure in the dialysate chamber” shall be understood as such that the pressure in the dialysate chamber is higher than in the blood chamber.

  The filling of the dialysate chamber and / or blood chamber is typically performed using a priming fluid, for example using dialysate or saline.

  The blood chamber is not yet filled when an overpressure occurs, so it is still gas filled and typically air filled. Therefore, the membrane surface on the blood chamber side is not wet. Unless the typically hydrophobic membrane is wetted on both sides, it has a high barrier effect against water-based priming fluids. Thus, overpressure can accumulate in the dialysate chamber.

  Here, if each area of the dialysate chamber side surface is also not wet due to undesirable air inclusions, the membrane will still dry locally before overpressure occurs, i.e. under the air inclusions. ing. Typically hydrophobic membranes have a high gas permeability, especially air permeability, in such a dry state.

  Air inclusions located on the face of the membrane on the dialysate chamber side can therefore be pushed through the membrane into a blood chamber that is not yet filled and can be moved by prevailing overpressure.

  The dialysis membrane is therefore permeable to air as long as it is still dry, as is the case with air-containing materials. Overpressure in the dialysate chamber ensures that residual air is still forced through the membrane into the empty blood chamber. The time savings due to improved ventilation is the method according to the present invention over some known flow-controlled filling processes directed to more rapid filling and to keep the air content in the dialysate chamber as low as possible. It can be achieved by carrying out the (pressure-controlled filling method) afterwards.

  The semipermeable dialysis membrane is preferably a membrane having hydrophobic properties at least in the dry state.

  In an embodiment, the overpressure is in the range up to 2 bar. The overpressure is preferably between 50 and 500 mmHg. Preferred ranges include a range between 140 and 220 mmHg, particularly a range between 175 and 195 mmHg. These overpressures are small enough to force air inclusions through the membrane and at the same time do not cause any damage to the filter.

  In an embodiment, the blood chamber is vented towards the environment during the occurrence of overpressure. When the blood chamber is vented towards the atmosphere, residual air passing over can escape and therefore no back pressure can accumulate.

  In an embodiment, the dialysate chamber is connected to the fluid guidance system on the infeed side and / or the return side during the performance of the method. Preferably, a provision is made that the dialysate chamber is integrated into the dialysate circuit of the dialysis machine.

  It can be provided that the blood chamber is also pre-integrated in the blood circuit of the dialysis machine during the execution of the method.

  The method is preferably carried out during the priming procedure of the fluid guide line in the dialysis machine. The method is preferably carried out automatically or after user input using the control unit of the dialysis machine.

  In an embodiment, the overpressure is generated by the closing of a valve located on the return side of the dialysate chamber and by the simultaneous delivery of additional fluid from the feed side of the fluid guidance system into the dialysate chamber.

  Further fluid transfer from the feed side of the fluid guidance system into the dialysate chamber can be effected by a pump and / or by a balancing system such as a balancing chamber present in the dialysis machine anyway. In particular, a feed pump arranged in the feed line can be used. The use of ultrafiltration pumps or return pumps located in the return line of the dialysis machine is also contingent on their suitability for this purpose, provided that a closed circuit is formed during priming or flushing. .

  In embodiments, any desired valve located in the dialysate circuit on the return side of the dialyzer can function as a return valve. In any case, it is possible to use a valve present in the return line, or a valve specifically provided for carrying out the method according to the invention.

  Measurement of pressure in the dialysate chamber can be made, for example, by a pressure sensor located between the pump and the dialysate chamber, between the dialysate chamber and the valve, or on the dialyzer itself.

  In an embodiment, pressure accumulation is stopped after reaching a predetermined overpressure value in the dialysate chamber. This can be achieved, for example, by stopping the pump. The predetermined overpressure value can be in the above-mentioned range.

  In an embodiment, the overpressure in the dialysate chamber is maintained for the ventilation period after the pressure build-up is stopped. This can be achieved, for example, by keeping the valve closed. Maintaining overpressure does not mean that the pressure remains constant in the dialysate chamber over the vent period. Rather, a pressure drop results from the escape of air inclusions located in the membrane or due to other effects.

  In an embodiment, the prevailing pressure and / or history within the dialysate chamber is measured during pressure build-up. Alternatively or in addition, the prevailing pressure in the dialysate chamber and / or its history can be measured during the venting period.

  In an embodiment, the measured pressure profile characteristic during the venting period is used to selectively initiate a repeat process or continuation of the priming procedure. Continuation of the priming procedure shall be understood as, for example, a dialysate chamber flushing procedure that follows the method according to the invention or a blood chamber filling that follows the method according to the invention.

  This characteristic can further define that it is used to output a signal representative of the ventilation status of the dialysate chamber.

  This characteristic can be an increase in the pressure / time curve or the duration until partial or complete depletion of overpressure.

  The steps shown can be performed automatically by the control unit of the dialysis machine.

  Alternatively or additionally, for example, it can also be determined gravimetrically whether air content is still present in the dialysate chamber.

  In an embodiment, the characteristic associated with the pressure history measured during pressure buildup is compared to a corresponding stability criterion that represents the integrity of the dialysis membrane and / or the integrity of the dialysate chamber interface with the fluid guidance system. Is done. A warning signal is issued by the machine for deviations in characteristics from the stability criteria.

  This characteristic can be, for example, the maximum fluid supply required to accumulate a particular pressure in the dialysate chamber.

  The method according to the invention is performed anyway before the start of dialysis therapy when the patient is not yet connected to the machine.

  The present invention further relates to a dialysis machine having a dialysate circuit, a dialysate chamber integrated in the dialysate circuit, a blood chamber, and a dialyzer having a semi-permeable dialysis membrane separating the two chambers. . The dialysis machine is characterized according to the invention in that it has a control unit that is configured to carry out the method according to the invention.

  Further details and advantages of the invention result from the following embodiments described with reference to the figures. The figure shows the following.

1 is a schematic view of a fluid induction system of a dialysis machine. FIG. 3 shows the time history of the fluid pressure in the dialysate chamber during the execution of the method according to the invention.

  FIG. 1 shows a schematic diagram of a fluid guidance system of a dialysis machine.

  The fluid induction system includes a dialysate circuit 1, a blood circuit 2, and a dialyzer 3. The dialyzer includes a dialysate chamber 4, a blood chamber 5, and a semipermeable membrane 6 that separates the dialysate chamber 4 and the blood chamber 5 from each other. In a typically used capillary dialysis machine, the blood chamber 5 is formed by the entire inner volume of the hollow fiber and the dialysate chamber 4 is formed by the inner space of the dialyzer housing surrounding the hollow fiber.

  The flow direction of the priming fluid or dialysate in the dialysate circuit is represented by the arrow 1c in the figure.

  The feed valve 7 is disposed in the feed line 1a of the dialysate circuit 1, and the return valve 8 is disposed in the return line 1b. The two valves are placed in the immediate vicinity of the dialyzer 4 in the illustrated embodiment, each representing the nearest actuator. The feed pressure sensor 9 is arranged in the feed line 1a of the dialyzer 3 and contributes to the determination of the fluid pressure on the feed side and the fluid pressure in the dialysate chamber 4 of the dialyzer 3 in the case of the closed return valve 8. .

  The feed line 1a is for performing any of the feed side of the balance chamber 10, the vent valve 11, the sterilizing filter 12, the conductivity and temperature measurement arrangement 13, and the pressure maintenance test in the order specified in the flow direction. And a maintenance valve 14. The feed pressure sensor 9 is disposed between the maintenance valve 14 and the feed valve 7.

  The return line 1b is divided into three parts between the first branch point 15 and the second branch point 16, and the first branch 17 is in the order specified in the flow direction, and the return side of the return pump 18 and the balance chamber 10 Including. The second branch 19 includes an ultrafiltration pump 19 a and does not pass through the balancing chamber 10. The third branch 20 includes a simple auxiliary valve 21. The return pressure sensor 22 is disposed in front of the branch point 15. The shut-off valve 23 is disposed after the second branch point 16.

  A bypass line 24 including a bypass valve 25 is further disposed between the feed line 1a and the return line 1b. The bypass line 24 branches from the feed line 1 a between the measurement arrangement 13 and the maintenance valve 14 and opens into the return line 1 b between the return valve 8 and the return pressure sensor 22.

  A stay line 26 having a stay valve 27 is further provided and connects the stay side of the sterilizing filter 12 to the return line 1b. The stagnant line opens into the return line 1b between the bypass line 24 and the return pressure sensor 22.

  A feed pump, not shown in more detail in the figure, and arranged in the feed line 1a on the feed side of the balance chamber 10 carries the priming fluid or dialysate into the feed line 1a and the dialyzer and according to the invention Contributes to accumulating pressure in the dialysate chamber within the method framework.

  The blood circuit 2 includes an arterial line 2a and a venous line 2b, and the dialyzer 3 is connected on the counterflow principle. The arterial line 2a includes an arterial pressure sensor 28, a blood pump 29, and optionally an arterial bubble trap 30 in the order specified in the flow direction. The venous line 2b includes a venous bubble trap 30a and a bubble detector 31 plus a venting device 32 and a venous clamp 33 in a specified order. The ventilation device 32 includes a ventilation line 34, a ventilation pressure sensor 35, and a ventilation valve 36.

  The dialysate chamber 4 of the dialyzer 3 is filled in a known processing framework prior to performing the method according to the invention to remove air content. In the illustrated embodiment, the filling is performed within an online processing framework and the dialyzer 3 is connected to the dialysate circuit 1 of the dialysis machine. Alternatively, filling can also be performed using a saline bag.

  The method starts after filling the dialysate chamber 4 and before filling the blood chamber 5. The blood circuit 2 including the blood chamber 5 is still filled with air when performing the method.

  Within the framework of the method, the feed valve 7 is initially held open and the return valve 8 is closed. A pressure-controlled filling program is started which carries additional priming fluid through the feed line 1a into the dialysate chamber 4 using a feed pump. Since the return valve 8 is closed, an overpressure for the blood chamber 5 where the environmental pressure prevails accumulates in the dialysate chamber 4.

  The overpressure generated with respect to the environmental pressure is detected using the feed pressure sensor 9. For example, in a state where a predetermined overpressure of 150 mmHg is reached, the fluid infeed is stopped, and the pressure history or pressure loss measured by the feed pressure sensor 9 is observed during the ventilation period. When air flows out of the dialysate chamber 4 and through the membrane 6 into the blood chamber 5, the overpressure in the dialysate chamber 4 causes the dried membrane 6 to exhibit a relatively low flow resistance to air. Again, it decreases rapidly.

  Bubbles are depicted in FIG. 1 with reference number 50 and the direction of flow from dialysate chamber 4 into blood chamber 5 is indicated by arrow 51.

  In order to prevent back pressure against the atmosphere from accumulating in the blood chamber 5, the blood chamber 5 is brought into the atmosphere, for example by the end of the arterial line 2a and / or the venous line 2b or by the vent line 34 having an open vent valve 36. Ventilated towards.

  If the overpressure drops rapidly in the dialysate chamber 4, it accumulates again. If the overpressure in the dialysate chamber 4 does not drop or only drops very slowly, this means that any residual air is no longer present in the dialysate chamber 4 or the residue that was initially present. This means that the air has already been largely pushed into the empty blood chamber 5.

The time course of the liquid pressure in the dialysate chamber 4 determined experimentally within the experimental framework is shown in FIG. The fluid pressure in the dialysate chamber 4 measured by the feed pressure sensor 9 is input in mmHg on the ordinate in the figure, and the time in minutes is input on the abscissa. At time t _INIT , the return valve 8 was closed and the feed pump was further activated until an overpressure p _{MAX of} 185 mmHg was accumulated in the dialysate chamber. This overpressure was completely exhausted again relatively quickly within an aeration period t _VENT of about 2 to 3 minutes due to the passage of residual air from the dialysate chamber 4 into the blood chamber 5.

  This behavior is also facilitated by the hydrophobic properties of the membrane. As long as the blood chamber 5 of the dialyzer 3 is not yet filled and is therefore dry, the membrane has a high flow resistance to the aqueous priming fluid.

  In addition to aeration, the method according to the invention is also used by additional parameterization to determine the integrity of the dialysis membrane 6, or the integrity of the interface of the dialyzer 3 with the feed line 1a and the return line 1b. be able to. For example, a stability criterion is defined here, which is the maximum fluid supply required to accumulate a particular pressure. If this stability criterion of volume restriction is not observed, conclusions can be drawn here about the possibility of membrane 6 tearing or interface leakage.

Claims (10)

A method of venting a dialyzer (3) having a dialysate chamber (4), a blood chamber (5) and a semi-permeable dialysis membrane (6) separating the two chambers,
The blood for removing air content (50) located on the surface of the membrane (6) on the dialysate chamber side after filling the dialysate chamber (4) and before filling the blood chamber (5) An overpressure on the chamber (5) is generated in the dialysate chamber (4).
A method characterized by that. The overpressure is in the range up to 2 bar, preferably in the range between 50 and 500 mmHg, preferably in the range between 140 and 220 mmHg, more preferably in the range between 175 and 195 mmHg.
The method of claim 1. The blood chamber (5) is vented towards the environment during the occurrence of the overpressure;
The method according to claim 1 or 2. Said dialysate chamber (4) is connected to the fluid guidance system (1) on the infeed side and / or return side during the performance of the method and is preferably integrated in the dialysate circuit (1) of the dialysis machine; The overpressure is caused by closing the valve (8) located on the return side of the dialysate chamber (4) and from the feed side (1a) of the fluid induction system (1) into the dialysate chamber (4). The provision is preferably made that is generated by the simultaneous transport of further fluids to
4. A method according to any one of claims 1 to 3. Pressure build-up is stopped after reaching a predetermined overpressure value (p _MAX ) in the dialysate chamber (4), preferably by stopping the pump (29).
5. A method according to any one of claims 1 to 4. The overpressure in the dialysate chamber (4) is maintained over the venting period (t _VENT ) after stopping the pressure buildup, preferably by keeping the valve (8) closed.
6. A method according to any one of claims 1-5. The prevailing pressure in the dialysate chamber (4) during pressure buildup and / or during the venting period (t _VENT ) and / or its history is measured;
7. A method according to any one of claims 1-6. The characteristics of the measured pressure history during the venting period (t _VENT ) are determined by the repetition of the method or priming procedure, eg the flushing procedure of the dialysate chamber (4) and / or the filling of the blood chamber (5). Used to selectively initiate a continuation,
The method of claim 7. The characteristics associated with the measured pressure history during the pressure build-up are the integrity of the dialysis membrane (6) and / or the fluid guidance system (1) at the interface of the dialysate chamber (4). Compared to the corresponding stability criteria that represent,
A warning signal is issued for the deviation of the characteristic from the stability criterion;
The method according to claim 7 or 8. Dialysate circuit (1), dialysate chamber (4) integrated in dialysate circuit (1), blood chamber (5), and semi-permeable dialysis membrane (6) separating these two chambers A dialysis machine having a dialysis machine (3),
Control unit storing an algorithm for performing the method according to any one of claims 1 to 9,
A dialysis machine characterized by comprising:

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